Field of the Disclosure
The present invention relates to a touch detecting circuit and a semiconductor integrated circuit using the touch detecting circuit, and particularly to a touch detecting circuit and a semiconductor integrated circuit using the touch detecting circuit that can be appropriately used for a touch panel control circuit which is connected to a touch panel that is overlapped with and mounted over a display panel.
Description of the Related Art
A touch panel is overlapped with and mounted over a display panel that is used for a smart phone or a tablet terminal, and a user can operate an apparatus by touching (contacting or tracing) a display screen using a finger or the like. In order to detect the touched position, various types have been proposed. For example, in a capacitance type, the touched coordinates are detected by detecting a change of a capacitance value caused by a finger or the like approaching a sensing capacitor that is disposed on a touch panel in a matrix. The capacitance type includes a mutual capacitance type and a self-capacitance type. In a state where one of electrodes that form a sensing capacitor is set as a transmission side and the other one of the electrodes is set as a reception side, the mutual capacitance type uses a phenomenon in which a coupling capacitance value that is generated between the transmission side and the reception side is decreased by an approach of a finger or the like. In a state where one electrode of a sensing capacitor is set as a ground potential, the self-capacitance type uses a phenomenon in which capacitance that is generated by approach of a human finger or the like which is grounded is added to the sensing capacitor, and thereby a capacitance value of the sensing capacitor is increased.
In JP-A-2011-14527, a touch detecting circuit of a self-capacitance type is disclosed. Electrodes in an X direction and electrodes in a Y direction are respectively arranged in a lattice pattern, and a sensing capacitor is formed at an intersection. A charging operation and a subsequent discharging operation are performed with respect to a capacitor that is selected by a combination of the electrodes in the X direction and the Y direction, and then a change of a capacitance value is detected.
In JP-A-2013-242699, a touch detecting circuit in which a self-capacitance type and a mutual capacitance type are combined is disclosed. When a multi-touch state is detected by the self-capacitance type, touched coordinates are detected by focusing only electrodes which are found to be in the multi-touch state using the mutual capacitance type detection.